Conventionally, there have been air conditioning controlling systems that control flow rates of hot and cold water to an air conditioner (referencing, for example, Japanese Unexamined Patent Application Publication Nos. H11-211191 and H06-272935). In these air conditioning controlling systems, flow rate controlling valve are provided in the supply routes for hot water/cold water to the air conditioner, where the valve unit within the flow rate controlling valve is driven to adjust the amount of opening of the flow path through which the hot/cold water flows.
Normally, in a flow rate controlling valve, an opening setting (a valve opening setpoint) is inputted from the air conditioning controlling device, and with the measured opening of the valve unit, detected by a valve opening detector, as a valve opening a measured value, the valve unit is driven so as to cause the valve opening measured value to match the valve opening setpoint.
For example, with the flow rate controlling valve disclosed in Japanese Unexamined Patent Application Publication No. 2009-245096, a motor is provided for rotating a valve rod that is connected to a valve unit, and a valve opening detector is provided for detecting the actual opening of the valve unit from the rotational position of the valve rod, where the measured opening of the valve unit, detected by the opening detector, and the valve opening measured value is used as a valve opening measured value, and the amount by which the valve rod is rotated by the motor is controlled so that this valve opening measured value will match the valve opening set point.
However, with the flow rate controlling valve (rotary valve) of the type that rotates a valve rod that is connected to a valve unit, as disclosed in Japanese Unexamined Patent Application Publication No. 2009-245096, the valve rod becomes twisted due to the pressure of the fluid that is flowing. That is, when a front-back differential pressure (fluid pressure) is reduced, this pressure acts on the valve unit, and produces a frictional force between the valve rod and the bearing that supports the valve rod. This frictional force produces a torque in the valve rod, and a twist is produced in accordance with this torque.
When a twist is produced in the valve rod, this produces an error between the measured opening of the valve unit (the valve opening measured value) and detected from the rotational position of the valve rod and the actual opening of the valve unit (the valve opening actual value). Because of this, this produces an error between the actual opening of the valve unit (the valve opening actual value) and the desired opening (the valve opening setpoint), which has a negative effect on the accuracy with which the opening is controlled.
The present disclosure is to solve problems such as described above, and the object thereof is to provide a rotary valve able to achieve high-precision opening control.